1. Field of the Invention
The present invention relates to an iron-based sintered material obtained by sintering an iron-based powder and a production method thereof, and in particular to an iron-based sintered material favorable for use as a member demanding fatigue strength and rigidity such as connection rod and a production method thereof.
2. Description of the Related Art
Connector ring rod (connection rod) for automobile engine is a member for connecting piston to crank shaft, and, as shown in FIG. 7, a connection rod 70 has an insertion hole 71 for insertion of a piston pin formed at one terminal and another insertion hole 72 for insertion of crank shaft pin at the other terminal.
Because of productivity and others, such a connection rod is often produced from an iron-based sintered material by powder metallurgy. Recently, there are demands for reduction in the weight and also in the thickness of the connection rod, in the trend toward further improvement in environmental resistance and performance of automobiles. However, reduction in thickness of the connection rod is occasionally accompanied by insufficient strength of the connection rod.
Under the circumstances above, for example, proposed as the material for connection rod is an iron-based sintered material in an iron-based metal structure containing nickel (Ni), copper (Cu), molybdenum (Mo), and carbon (C) in amounts in particular ranges and having a void rate of 2 to 8% in the metal structure (see Japanese Patent Application Laid-Open No. 2002-20847).
The iron-based sintered material described in Japanese Patent Application Laid-Open No. 2002-20847, which contains the elements at particular rates and is obtained by sintering the iron-based powder to make the iron-based powder have a particular void rate, has improved strength and toughness.